stdarg x86_64 problems...

[John Colvin]

When I compile the following code with -m32 and -m64 i get a 
totally different result, the documentation suggests that they 
should be the same...

import core.stdc.stdarg, std.stdio;

void main() {
	foo(0,5,4,3);
}

void foo(int dummy, ...) {
	va_list ap;
		
	for(int i; i<10; ++i) {
		version(X86_64) {
			va_start(ap, __va_argsave);
		}
		else version(X86) {
			va_start(ap, dummy);
		}	
		else
			static assert(false, "Unsupported platform");
		
		int tmp;
		va_arg!(int)(ap,tmp);
		writeln(ap," ", tmp);
	}
}

when compiled with -m32 I get:

FF960278 5
FF960278 5
FF960278 5
FF960278 5
FF960278 5

and with -m64 I get:

7FFFCDF941D0 5
7FFFCDF941D0 4
7FFFCDF941D0 3
7FFFCDF941D0 38
7FFFCDF941D0 -839302560

(the end stuff is garbage, different every time)

I'm uncertain, even after looking over the stdarg src, why this 
would happen. The correct output is all 5s obviously.